The desire to both increase the gas mileage of vehicles and decrease the amount of pollutants emitted by vehicles has lead led to the development of hybrid electric vehicles (HEVs). HEVs use a combination of an internal combustion engine and an electric motor to power the vehicle. Different types of HEVs exist. Parallel hybrid vehicles use an internal combustion engine in tandem with a battery powered electric motor to propel a vehicle. Serial hybrid vehicles use a battery powered electric motor to propel a vehicle and a secondary power source, such as a fuel cell or internal combustion engine, to recharge the battery. A third type of hybrid vehicle, known as a start/stop hybrid, shuts down the internal combustion engine when the vehicle comes to a stop and utilizes a battery to power the vehicle system. In this configuration, when the vehicle starts to move again the internal combustion engines restarts.
Common to all of these types of hybrids is that the on-board batteries become discharged and, therefore, need to be charged. Typically, there are two different ways to charge the battery. The first way is to use regenerative braking to charge the battery. In regenerative braking, when the electric motor provides braking torque, energy is produced to recharge the battery.
The second way to charge the battery is through the use of active charging. In active charging, the internal combustion engine uses the electric motor as a generator to charge the battery. In order to maximize the efficiency of the HEV, active recharging of the battery should occur at times when the engine is running efficiently. Therefore, there is a need for a method and system for hybrid energy management control.